Variable universal life insurance policies do have a cash value account, but the cash value is not managed by the life insurance company at all. In contrary, the money is invested in variable sub-accounts, which are managed by third party fund companies. These sub-accounts are essentially mutual funds. Each sub-account has a stated objective, and the manager of the account actively invests in a portfolio of underlying securities that match the stated objective.
The policy owner has the option to the invest the money as they see fit. They can make trades between the sub-accounts, and they can allocate money to various funds in whatever way they decide. The performance of the policy will be dictated by the performance of the funds. The funds performance is affected by the underlying assets. For instance funds may be large cap stocks, mid cap stocks, small cap stocks, short term bond funds, mixed bond funds, treasury security funds, commodities funds, ect, and each fund will own assets within the asset class. Most variable sub-accounts act as a proxy for mutual funds which are available to the public, and they are managed by the same fund companies.
The life insurance company does not participate in earnings from these funds. Rather, they collect a small percentage fee based upon the total assets in the funds from the VUL policies, in addition to the insurance charges deducted from the policy. Because the owners are not actively invested in the life insurance company they deemed not to be able to take part in the earnings. VUL policies are not considered to have an ownership share, and therefore are nonparticipating policies in most all cases.